Differential signaling is known in the art as a method of transmitting information electronically by means of two complementary signals sent on two separate traces in which a receiving device reads the difference between the two received signals. A driver circuit is generally used to provide the differential signal to be transmitted to the receiver circuit.
Low power high-speed current steering logic (LPHCSL) drivers are known in the art as a means of providing differential signaling. In contrast with traditional HCSL, which steers a constant current between true and complement outputs of a differential pair, low power HCSL (LPHCSL) uses a push-pull voltage drive instead of a current drive. Current consumption is reduced in a programmable LPHCSL driver because supply current flows in the driver only during the round trip flight time, which is equivalent to the time required for a rising edge of the signal from the LPHCSL driver to be received at the receiver and the time required for the signal to be returned back at the driver.
Current architectures of LPHCSL drivers have limitations on the range of the supply voltage of operation. Additionally, LPHCSL driver designs currently known in the art provide multiple driver impedances by adding and/or subtracting driver legs, which has a negative impact on the die area and increases the complexity of the device for slew rate control and impedance load matching.
Accordingly, what is needed in the art is a programmable LPHCSL driver circuit having an improved supply voltage range and a higher degree of programmability for impedance matching that does not negatively impact the die area required for the circuit.